The invention relates to dressings and in particular, to dressings for wounds in the oral cavity and for delivering preparations, such as antibiotics, pain medication, or agents for whitening the teeth, to selected parts of the body including the oral cavity and other parts, and to materials which can applied to the wound area to protect the wound
Conventional dressings for the oral cavity has not been fully satisfactory. The oral cavity has a high level of bacteria and thus, wounds, including ulcers cannot be adequately treated. Frequently, the wounds take several days to heal and if patients are to be sent home after the surgery, they need to eat during the healing time. This presents additional problems in constructing an appropriate dressing. Various methods of protecting the wound often result in slowed healing around what is commonly a plaster-like material used to cover the wound. This plaster-like dressing can become detached and there is then renewed possibility for infection and bleeding.
It is often necessary to deliver an antibiotic or other pharmaceutical, drug or preparation to a wound or to apply whitening agents to the teeth. However, when such preparations are applied within the oral cavity, it can be difficult to maintain the preparation in its proper location in view of the natural processes which occur within the mouth.
Accordingly, it is desirable to provide an improved wound dressing and system for applying drugs and other treatment preparations to wounds, which overcome the disadvantages of the prior art.
Generally speaking, in accordance with the invention, a dressing material and method of treating wounds and applying therapeutic materials and preparations to selected parts of the body is provided. The dressing can comprise a water-soluble polymer which is capable of forming a viscous aqueous or non-aqueous solution and form a gel. The gel can be dehydrated to form a foam or powder which can be reconstituted prior to use, or applied directly to a wound. The dressing can be constructed in the form of a sponge or sheet impregnated with the gel, or coated onto a substrate or backing. The dressing can also be provided in a form of a dehydrated powder, such as one which can be sprinkled under a flap of tissue and which will hold the flap down as a substitute for the use of stitches. Wounds treated with dressings in accordance with embodiments of the invention will tend to heal faster because there is less trauma to the wound or surgical site and because dressings in accordance with the invention do not interfere with healing the body, which can heal at a rapid rate.
Gels in accordance with the invention can comprise acrylic acid polymers, particularly acrylic acid polymers cross-linked with divinyl glycols, and in particular, pharmaceutical resins sold under the name NOVEON, by B. F. Goodrich, Chemical Co. and most preferably the acid form of polycarbophil, meeting the USP monograph for polycarbophil. The general structure of such a resin is the following: xe2x80x94[xe2x80x94CH2xe2x80x94HCCOOHxe2x80x94]n,xe2x80x94 and is drawn below. 
The gel can also be formed with preservatives, such as sorbic acid, hydroxides, such as sodium hydroxide and water. In use, the gel, gel in a carrier or gel, carrier and backing can adhere to gum surfaces and is easily removed by direct removal or washing.
Coatings may be applied to a wound, or the dressing may be incorporated onto a backing such as a tape or adhesive plastic strip to further protect the dressed wound from mechanical disturbances. The backing may be of a porous, non-porous or micro-porous material. For protection in an excessively fluid environment, a non-porous barrier can be applied to the area of the dressed wound to protect the dressing from fluids, such as saliva, which can compromise the adhesiveness of the dressing.
Accordingly, it is an object of the invention to provide an improved wound dressing.
It is another object of the invention to provide an improved method of treating wounds.
It is another object of this invention to provide a method of protecting the dressing being used to treat the wound.
Still another object of the invention is to provide an improved method and composition for treating wounds in the oral cavity.
The invention provides a biodegradable matrix in the form of gel formulations and methods for producing the same, which also have the ability to contain, carry and apply chemical elements, such as antibiotics, anti-bacterial agents, bacterial-static agents and other drugs, for preventing or treating infection and to promote, enhance and speed the healing of wounds. The invention also comprises a carrier for the gel formulation, such as a gauze, sponge or other sheet that can become impregnated with the gel formulation and further processing by steps of severe dehydration, such as that associated with lyophilized processing to provide the gel formulation in powder form. The gel and/or gel/carrier composite can also be provided on a backing to protect the dressed wound, or the dressed wound can be protected by coating the wound site with a tissue adhesive such as cyanoacrylate.
The formulations and articles described herein are particularly useful for topical applications within the oral cavity, but alternatively may be used elsewhere on the body. The formulations comprise water soluble, pharmaceutically and/or oral cavity compatible polymeric material for providing viscosity within acceptable ranges, as determined by the particular application of the gel. The gel formulation provides advantageous controlled release and increased contact time with the intended oral cavity site. Preparing and using therapeutic gels is discussed in U.S. Pat. Nos. 5,876,744 and 5,989,535, which themselves cite earlier patents on this issue and the contents of these patents are incorporated herein by reference.
Gel/carrier and gel/carrier/backing formulations of the present invention have the advantage of adhering to a gum or tooth surface and conforming to the irregular surface contours and membranes encountered within the oral cavity. The gel and composites comprising the gel with the carrier and/or backing may be applied directly to the gum or tooth surface or in conjunction with or without a compliant non-porous, porous or micro-porous substrate, for example, in the form of a coating, to be applied to the oral cavity site intended for specified activity. Composites in accordance with preferred embodiments of the invention have the further advantage of easy application to the oral cavity surface and easy removal by direct removal or washing. Embodiment of the invention can also exhibit the ability to permit increased activity to the intended site and further activity increase through moisture activation of components, if required.
When the dressings of this invention are applied to the wet surface of a wound, the gel or gel/carrier adheres to the wet tissue. In this manner, a wound can be closed or sealed by the adhesive effect of the dressing. The adhesiveness of the gel or gel/carrier can be compromised, however, if the material becomes totally engulfed in fluids. To protect the dressing from the effect of an overly wet environment, the dressing can be applied in a manner disclosed herein, and then a coating or non-porous backing may be adhesively applied to protect the dressing from additional fluid from the wet environment.
In the oral cavity, for example, the dressing material may be placed over the wound or within a flap of wound tissue, and a polymeric coating, such as of cyanoacrylate applied. Such coatings may be in the form of a spray, or a liquid to be applied by pouring or otherwise applying to cover the dressed wound. Said coating protects the dressing from additional fluids, so that the adhesion of the dressing is not compromised. Also, when used in the oral cavity, such coatings protect the dressing from mechanical disturbance such as from the tongue, cheek or the chewing of food. Alternatively, a non-porous, porous or micro-porous covering, such as a tape or plastic adhesive strip may be affixed to the area to protect the dressing.
On the skin or other areas of the body, the dressing may be applied to the wet tissue of a wound to close or otherwise seal the wound. The adhesiveness of the dressing is very effective in closing and protecting the wound. However, a wound may be subject to external mechanical disturbances which may act to overcome the adhesive properties of the dressing and thus open the wound. Such mechanical disturbance may consist of a force from flexing or stretching the surrounding tissue, or rubbing against an external object, or other insult.
The dressing of this invention may be attached to or inserted onto an adhesive backing, such as a tape or plastic adhesive strip or other similar substrate. The tape or substrate will fix the dressing to the wound and provide added protection against such mechanical disturbance. The use of a plastic strip or other substrate to which the dressing material is affixed will allow the dressing to last longer and the wound to heal quickly.
The use of a non-porous, porous or micro-porous substrate can be effective in protecting against the mechanical disturbances such as those described above. If a non-porous covering or substrate is used, the fluids of the wet wound tissue will be held within the dressing and be reabsorbed. A porous substrate may be such as a tape or plastic adhesive strip which has air holes. Such a porous substrate will allow the wound to breath and dry, thus maintaining or increasing the adhesiveness of the wound during healing.
Aqueous gels in accordance with preferred embodiments of the invention will have different viscosities depending on the intended application. The viscosity of gel material prior to the freeze dried processing can have significant effects for a number of reasons. A thinner low viscosity gel in the range of about 1,000 cps up to approximately 10,000 cps, will generally have a lower concentration of solids. The lower concentration of solids in solution can result in a thinner freeze dried product when compared to the same processing steps, lyophilization, applied to a thicker gel, with high viscosity in the range about 10,000 cps to 100,000+ cps, which generally have a higher concentration of solids in solution. Thus, adjusting the viscosity lends itself to the custom or tailored fabrication of the solid foam, porous sheet or resulting product. This would allow thicker materials to be utilized in extended time release of drug or preparation of delivery products.
This would also allow thicker materials to fill larger void zones of the oral cavity intended for coverage. This would also lend the thicker product to potentially be less flexible and compliant to contours within the oral cavity where the wound dressing may be required. The thickness may benefit the product efficiency in the prevention of detritus permeation through the dressing to the covered site.
It should also be noted, that this product, regardless of initial thickness, after primary processing (freeze drying), may be pressed via a secondary process step after the completion of the freeze drying procedure. This additional step would allow the physical characteristics, and potential flexibility benefits of a thinner product to be experienced by a xe2x80x9cthickerxe2x80x9d freeze dried product, resulting in what may be considered a concentrated product formulation or processing step.
The solubility of the material may be adjusted through the addition of non-interacting secondary raw materials to the liquid state formulation mix, or sprayed over the completed product to form a bi-layer, tri-layer, or other multiple layer material that can demonstrate varied solubility and degradation over time when compared to a single formulation mix and subsequent freeze drying or other means of processing to form the desired product.
Gel forming materials in accordance with preferred embodiments of the invention can comprise water-soluble polymers capable of forming a viscous aqueous solution of a non-water soluble material. Water-swellable polymers, which can also form a viscous solution are also preferred. As used herein, the terms swellable polymers will refer to those polymers which absorb water rather than dissolve in water. Cross-linked forms of the polymers described herein may not be water soluble, but may be water swellable. As used herein, cross-linking encompasses, but is not limited to covalently bonding polymer chains with bifunctional reagents. It will also be understood by those of ordinary skill in the art that certain polymers may have to be used in the salt or acid form or a partially neutralized form in order to be made water-soluble or to obtain the viscosity characteristics devised by a specific application. Thus, unless otherwise specified, the identification of a polymer will also refer to the salt, acid or chelated form of the polymer. Preferred dressings will be able to adhere to a wound site, such as one within the oral cavity for at least 24 hours.
Preferred polymers for forming aqueous gel formulations in accordance with preferred embodiments of the invention include vinyl polymers, polyoxyethylene-polyoxypropylene copolymers, polysaccharides, proteins, poly(ethylene)oxides, acrylamide polymers and derivatives and salts thereof. It is also to be understood that poly(ethylene)oxides includes polyethylene glycol. For applications in which ingestion of the formulation may occur, it is preferred not to employ polyoxyethylene polyoxypropalene copolymers or poly(ethyleneoxide).
Vinyl polymers, also known as substituted polyethylenes, are useful in accordance with the preferred embodiments of the invention and may be selected from polyacrylic acid, polymethacrylic acid, polyvinyl, tyrrolidone and polyvinyl alcohols.
One particularly advantageous family of gel forming polymers is in the family of acrylic acids and methacrylic acids, particularly when cross linked with divinyl glycols and particularly 3,4-dihyroxy-1,5-hexadiene, in view of several factors, including high water absorbing ability. One particularly preferred polymer in this family is polycarbophil, most preferably the acid form, and sold by B. F. Goodrich under the designation NOVEON AA-1. Polycarbophil is preferably present as at least 0.1, advantageously 0.1 to 2.0 and more preferably 0.3% to 0.7% by weight of the gel formulation prior to any dehydration thereof.
The polysaccharides in accordance with preferred embodiments of the invention may be selected from cellulose or cellulose derivatives, (such as carboxymethylene, carboxymethylocellulose, and/or plasticized methyl or ethyl cellulose), glycoaminoglycans, agar, pectin, alginic acid, dextran, starch, and chitosan.
Starches occur in two forms, the alpha-amylose and amylopectin form. The more water soluble alpha-amylose form is preferred. Glycosaminoglycans in accordance with preferred embodiments of the invention can be selected from hyaluronic acid, chonocroitin, chondroitain-4-sulfate, chondroitin-6-sulfate, sematan sulfate, deratan sulfate, heparin sulfact ena heparin. Cycosaminoglycans and polysaccharides are advantageously included in formulations in accordance with preferred embodiments of the invention, in order to enhance the tissue conditioning and protection of the gum-line in expanded application use. Proteins are advantageously included in formulations in accordance with preferred embodiments of the invention, including collagen, gelatin and fibronectin. Advantageous acrylamide polymers include polyacrylamide or polymethacrylamide polymers. Biocompatible polyacrylamide polymers are preferred.
Gels in accordance with preferred embodiments of the invention can be lyophilized to provide a stable powder, from which gels can be reconstituted at the time of use, for use directly on dry sheets, foam or films, to deliver a dosage of the gel to the intended site of application, such as in the oral cavity. Also, powdered gels can be sprinkled under flaps of skin to hold the flap in place and promote healing.
Gels and composites employing the gels and the further processing thereof are useful in drop formulations, irrigating solutions, protective dressings, salves, as in liquid and solid form for wound healing and the like. A wound that may be healed using the compositions disclosed herein can be those which result from accidental or medical injury, surgically induced wounds, such as surgery in the oral cavity, such as those related to dental applications and cutaneous wounds, such as burn wounds, incision wounds, donor site wounds from skin transplants, ulcers (cutaneous, decubitis, venous stasis and diabetic). The gels and related embodiments thereof, such as films of the present invention may also be used for healing internal incisions as well as internal wounds, such as gastric ulcers.
In those applications where the gel, films or sheet are applied to an internal or incision wound, it is preferred that the gel, film, or foam forming polymer be degradable. Natural occurring polymers, such as collagen, glycoaminoglycans, gelatin and starch are generally degradable. Cellulose and cellulosics are generally not degradable. Synthetic polymers, such as vinyl polymers are not degradable.
Viscosity for gel formulation in accordance with preferred embodiments of the invention, prior to lyophilization of the composites is generally between 1,000 cps to 12,000,000 cps at room temperature (RT). A preferred viscosity ranges between 10,000 and 100,000 cps at RT.
Acrylamide polymers, particularly those exhibiting adhesive characteristics, may be useful in oral cavity applications. In one embodiment of the invention, the formulation can comprise 0.1% by weight acrylic polymer as a thickening agent and demonstrate a viscosity range between about 13,000 and 30,000 cps. In another embodiment of the invention, 0.5% acrylic polymer as thickener is used in the formulation demonstrate a viscosity range from 40,000 to 60,000 cps. In a more preferred embodiment, the acrylic polymer is comprised of polyacrylic acid cross linked with polyvinyl glycol and in a most preferred embodiment, comprises the acid form of polycarbophil. The polymer component can also be used to contain the xe2x80x9cmedicinexe2x80x9d of the composition.
In another embodiment of the invention, the gel component may comprise 1-20% by weight cellulose derivative, having molecular weights from 5-700,000. In preferred embodiments, the cellulose derivative is present as 2-8% by weight and the preferred molecular weight range is from 50,000-300,000. Viscosities in the 10,000 to 200,000 cps range are also preferred. The preferred cellulose derivatives are hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), methyl cellulose (MC), and carboxymethyl cellulose (CMC).
It will also be apparent to one of ordinary skill in the art that the desired viscosity range can be achieved by varying both the molecular weight and the percent concentration of the polymer in the formulation. For example, a gel having a relatively low viscosity can be formulated by using a low molecular weight polymer or a lower percent concentration of a higher molecular weight polymer, or a combination of the two. Thus, higher viscosity gels can be achieved by raising either the molecular weight of the polymer, the percent concentration of the polymer or both.
The gel, foam and/or film formulations in accordance with preferred embodiments of the invention can be used to coat fibers of an absorbent gauze dressing, nonporous, porous, or micro porous fabric as identified below and provide dressings that can be placed in the oral cavity. The gels, foams or film formulations of preferred embodiments of the invention can be applied to the dressing material by soaking, spray coating, dip coating or applying the material to the dressing material by mechanical means, such as the use of a doctor blade or other conventional coating methods.
The composite dressing can be processed, for example, through severe dehydration, by e.g., lyophilization and applied to the intended surface. The activity of the contained xe2x80x9cmedicinexe2x80x9d, in applications where such product is intended to deliver the xe2x80x9cmedicinexe2x80x9d to an intended site, contacts the site to increase potential of intended activity.
The dressing material in accordance with preferred embodiments of the invention can include porous, non porous, or micro porous polyesters, rayons, cottons, wools, silks, papers, foams (open and closed cell), woven and non-woven fabrics, polyolefins, polyesters, copolyesters, polyurethanes, ethyl vinyl acetate, polyether block amides, ethylene methacrylic acids or polyethylenes. If applications in accordance with the invention required potential ingestion of the product, degradable components should be used and should be of pharmaceutical or medical grade material, such as those designated by USP, NF, P, NF, etc. The biodegradability of various polymers are known to those in the art.
The biodegradability of the various polymers may also be related to the water solubility of the products that are produced from these raw materials. The degradability of the products produced can be directly related to the water solubility and effect of ions, such as salts, and other chemical aspects that may come in contact with the product once in the oral cavity or other site of intended application. A non-water soluble component of the product, addition of other raw materials to the formulation prior to, or following the freeze drying process may affect the solubility of the final product produced. The non-soluble component could be utilized to extend the time duration and treatment at the intended site of application. The non-soluble component could become, and be designed to dissolve after certain time exposure to application site fluids or enzymes, or release soluble items within the product itself or influenced by or a direct production of the application site utilized, such as bodily fluids.